1. Field of Invention
This invention relates to a device and method for tapping tubing in a fluid or gas transportation system for the attachment of spur lines, valves, and other devices.
2. Description of the Related Art
Liquid transportation systems, such as irrigation systems, employ tubing to conduct liquid from a source to a different location. It is often desirable to divert some amount of liquid from the main line to spur lines or devices which use the liquid. One common method of diverting liquid from a main line is to introduce a T-fitting. T-fittings have at least three openings through which liquid may flow and they are added to the main line by severing the line at an appropriate location and inserting the T-fitting between the severed sections. Liquid may flow through the T-fitting and continue down the main line and some amount of liquid may be diverted from the main line through the stem of the T-fitting. The stem of the T-fitting may be attached to spur lines, valves, sprinklers, nozzles, or other devices which require liquid from the main line.
T-fittings have several disadvantages: they reduce the structural integrity of the system; they reduce the pressure in the down stream portion of the main line; and, they are prone to leaks. Because the main line is completely severed, the structural integrity is reduced and it is more susceptible to unintended separation. Liquid pressure and external forces can completely separate one of the sections of the main line from the T-fitting. T-fittings also reduce liquid pressure in the main line because they usually have a smaller inner diameter. This produces friction and turbulence in the stream of liquid and reduces pressure down stream of the T-fitting. Finally, T-fittings have a large amount of joint surfaces between which leaks can occur. Over the life of the T-fitting, leaks may occur which waste liquid and further reduce liquid pressure.
Other devices that are often used to divert water from a main line include tapping fixtures. Tapping fixtures are introduced into the main line by puncturing the wall of the line thereby creating a small hole. The fixtures are usually inserted into the hole or are held against the tube by a tapping device.
Tapping fixtures have several advantages over T-fittings. Tapping fixtures do not reduced the structural strength of the main line as much as T-fittings, they do not reduce the down stream pressure as much as T-fittings and they are less likely to leak. Unlike T-fittings, tapping fixtures do not completely sever the main line; only a small hole is required. Thus, the main line is stronger and less likely to separate. Tapping fixtures also do not reduce the diameter of the main line which helps to maintain the down stream pressure of the main line. Finally, tapping fixtures are less likely to leak because there are significantly less joint surfaces between which leaks may occur.
However, tapping fixtures do have disadvantages. Some tapping fixtures are inserted into a line and held in place only by ridges or teeth; no supporting structure is used. These kinds of fixtures tend to leak and work free of the tubing over time. It has been found that tapping fixtures are much more reliable if they are supported by a device which clamps the main line. Three such devices are disclosed in U.S. Pat. No. 5,170,813 to Francis, U.S. Pat. No. 5,345,964 to Friedel, and U.S. Pat. No. 5,353,831 to Roth. These devices generally help support tapping fixtures. Although these clamping devices are useful, they are bulky, have many parts, require many steps to install, are susceptible to corrosion, and are expensive to manufacture. For example, all of the devices utilize bolts to fasten the device to a main line. This requires the operator to go through several steps to attach the device to a main line. In addition, the user is required to carry wrenches to tighten the device which may be inconvenient. The bolts and other metal parts of these devices are also susceptible to corrosion.
Although the discussions above and below make reference to fluid transportation systems, such as irrigation systems, it is recognized that gas transportation systems are equally applicable. The problems encountered with T-fittings and tapping fixtures in fluid transportation systems are also found in gas transportation systems. The present invention may be used to solve these problems in both kinds of systems.